Baker Hughes Oilfield Operations LLC

Telecommunications Research Laboratories

Novatel Communications Ltd.

Xact Downhole Telemetry, Inc.

Baker Hughes, a Ge Compnay, LLC

Harris Canada, Inc.

Telecommunications Research Lab.

John Godfrey McRory

Paul L Camwell

John-Peter Van Zelm

James William Haslett

Andrew E McGirr

Xiaojun Xiao

James M Neff

David D Whalen

Robert James Davies

Bogdan Alexandru Georgescu

Holly Pekau

Darrell W Barabash

Paul M Camwell

Alan D McGrath

Christopher D Holdenried

Dave Whalen

A downhole acoustic transmitter has a piezoelectric transducer, an enclosure in which the piezoelectric transducer is housed, a transducer preload means which applies a selected compressive force against the transducer such that a mechanical preload is applied to the transducer, and an acoustic tuning element which has a first end coupled to the transducer preload means or the transducer, and an open second end. The acoustic tuning element is not coupled to anything but the transducer preload means or transducer, so the transducer preload means effectively has a second open end and thus can maintain the same preload compressive force on the transducer even when the transmitter is subjected to tension and compressive forces during operation.

Method and apparatus for pre-loading a piezoelectric transducer for downhole acoustic communication

A downhole acoustic transmitter has a piezoelectric transducer, an enclosure in which the piezoelectric transducer is housed, a transducer preload means which applies a selected compressive force against the transducer such that a mechanical preload is applied to the 5 transducer, and an acoustic tuning element which has a first end coupled to the transducer preload means or the transducer, and an open second end. The acoustic tuning element is not coupled to anything but the transducer preload means or transducer, so the transducer preload means effectively has a second open end and thus can maintain the same preload compressive force on the transducer even when the transmitter is subjected to tension and 10 compressive forces during operation.

Methods, systems, and techniques for controlling voltage applied across a piezoelectric stack of a downhole acoustic transmitter. At least one of the temperature of the stack and the compressive stress applied to the stack is monitored. At least one of the temperature of the stack and the compressive stress applied to the stack is compared to a temperature threshold and a stress threshold, respectively. When the stack signal is an alternating voltage signal and when at least one of the temperature of the stack and the compressive stress applied to the stack respectively exceeds the temperature threshold and the stress threshold, the stack signal is modified such that a negative polarity portion of the stack signal has a maximum magnitude less than a magnitude of a negative polarity limit.

Method and system for controlling voltage applied across a piezoelectric stack of a downhole acoustic transmitter

An acoustic transmitter for transmitting an acoustic signal through a downhole medium includes a voltage source; a composite load; and switching circuitry that applies voltage from the voltage source across the composite load in response to a drive signal. The composite load includes charge control circuitry, in the form of at least one inductor, connected electrically in series with a piezoelectric transducer that may be electrically modeled as a capacitor.

Acoustic transmitter for transmitting a signal through a downhole medium

A system and method of closed loop control whereby groupings of surface sonic transmitters disposed along the planned path of a well send sonic wave energy to a downhole sonic receiver (or alternatively a downhole sonic transmitter signalling to grouping of surface sonic receivers) in a manner that facilitates the downhole positioning of the well. Subsequent offset well positioning, relative to the first well, may be achieved in a similar manner.

System and method for accurate wellbore placement

A monolithic transformer compensated circuit with enhanced quality factor without significantly increasing noise levels is presented in this disclosure. The technique uses a monolithic transformer and a current source driving current into the transformer secondary winding to achieve loss compensation in the transformer primary. An ac current which is proportional to, and in phase with the voltage applied to the primary winding can be used to achieve theoretically perfect loss compensation at a given frequency in the RF (GHz) frequency range. Examples of circuit applications that are particularly suited to the technique include Voltage Controlled Oscillators (VCO's), Low Noise Amplifiers (LNA's) and Filters. The technique has the added advantage of reducing power consumption in some applications.

Monolithic transformer compensated circuit

A parallel-summation logarithmic amplifier is described that uses a novel topology of cascaded and parallel amplifiers to achieve extremely high bandwidth. Included in the topology is a unique delay matching scheme for logarithmic amplifiers that is amenable to fabrication in integrated circuit form. The result is flat group delay over broad frequency ranges and different power levels. The resulting log amplifier is suitable for radar applications and for use in high data rate fiber-optic networks. Also described is a unique design process that yields a set of amplifier gains that closely approximate a logarithm. Also described is the novel idea of using a parallel feedback amplifier (PFA) in piecewise-approximate logarithmic amplifiers. This innovation allows for the design of broadband amplifiers with significantly different gains and similar phase characteristics, which is extremely useful when designing high-frequency logarithmic amplifiers.

Logarithmic amplifier

A complex baseband model of the power amplifier within a DSP domain is used to develop a feedback signal that would be equivalent to the optimum negative feedback used for the analog amplifier. Once the feedback signal is available, it can be processed to compensate for the effects of the group delay and for optimum loop gain, hence resulting in a broadband response with no theoretical limitations on the linearization of the amplifier.

RF amplifier with feedback based linearization

An antenna for use with portable duplex radio transceivers, such as those found in hand-held cellular telephones, which includes a pair of co-planar radiating patch elements elevated above a conductive surface by a conductive bar. The surface and bar define a reference ground plane which inherently isolates the patches. The patches are shaped so that they operate in a desired frequency band as well as band-pass filters--one of the patches is tuned to the transmit band and serves a transmit structure, and the other patch is tuned to the receive band and serves as a receive structure. Switching devices such as positive-intrinsic negative (PIN) diodes can be disposed along the space between the patches and the ground plane to allow each structure to be tuned. The antenna is efficient, because of inherent isolation between the receive and transmit patches, and eases the front end filtering functions traditionally performed by a duplexer. It can be completely enclosed within the chassis of a hand-held telephone.

Duplexing antenna for portable radio transceiver

A cellular subscriber modem for receiving CCITT-type quadrature amplitude modulated (QAM) signals. The cellular modem includes a novel symbol detector that converts received symbol information to polar notation. The detector's constellation thresholds include a circular threshold having a radius greater than the magnitude of the innermost symbols, but less than the magnitude of the outermost symbols, and radially spaced thresholds, which further discriminate between the outermost symbols. As a result, special cellular-compatible modem equipment need not be connected between the public-access switched telephone network and the computer equipment at the other end, which means that a CCITT-compatible cellular subscriber modem can then be treated as any other type of CCITT-modem. The detector may be implemented in the software of a standard modem processor, or as several analog comparator circuits.

Growing community of inventors

Calgary, Canada

John Godfrey McRory